With talks on reaching a global pact on climate change at a critical juncture, governments are increasingly concerned about the impact of the issue on national security.

This year, for the first time, US national security agencies have begun to include potential worst-case scenarios resulting from climate change in their long-term planning.

Among those potential scenarios is the mass migration of millions displaced by flooding, drought and other effects of changing weather patterns.

Al Jazeera's Patty Culhane reports.